1. Field of Invention
The invention is directed to downhole tools having a sealing material disposed on an outer wall surface of the downhole tools and methods for securing a sealing material to the outer wall surface of the downhole tools.
2. Description of Art
Resilient sealing rings are widely used on the outer surfaces of downhole tools such as packers, space-out assemblies, anchors, and excluder subs. The sealing ring typically engages an outer tubular member, such as casing, in the well. The ring may be used to provide a seal or to provide a frictional surface on the outer surface of the tool to assist in positioning the tool within a bore of a well. The sealing material of the ring may also be used to provide a more flexible or expandable connection between two components of a downhole tool.
It is desired to secure the sealing material to the downhole tool such that the sealing material stays secured to the downhole tool. In some downhole tools, previously, the resilient material was secured to an outer diameter surface of a metal reinforcing ring of the downhole tool. When set, the reinforcing ring is expanded plastically beyond the yield strength of the metal of the reinforcing ring. The prior art tools used chemical bonding to secure the sealing material to the reinforcing ring. These chemical compounds, however, become less effective as the temperature increases, especially where the temperature increases above 400° F. As a result, the bond of the resilient material to the outer surface of the reinforcing ring is compromised and the resilient material is released from the outer surface of the reinforcing ring. Accordingly, the tool becomes inoperable or ineffective.
Additionally, fluids within the well that flow around and past the downhole tools, either flowing up the well or down the well, slowly undermine the chemical compound securing the sealing material to the outer surface of the metal reinforcing ring of the downhole tools. The flowing fluids may dissolve or otherwise prevent the chemical compound from maintaining its bonding capabilities. Further, the flowing fluids may force themselves, together with debris carried in the flowing fluids, between the interface of the sealing material with the metal surface of the reinforcing ring. Therefore, the flowing fluid, either alone or in combination with elevated temperatures within the well, can cause the bond of the sealing material to the metal surface of the reinforcing ring to weaken, thereby causing the seal to leak and, thus, rendering the tool inoperable or ineffective. As a result, costs are increased for replacing and repairing, if possible, the damaged downhole tool having an insufficiently secured sealing material to metal wall surface of the reinforcing ring.
Accordingly, prior to the development of the present invention, there have been no downhole tools having a sealing material secured to the metal outer wall surface of a radially expansible reinforcing ring that: increase the life of the downhole tool by increasing the length of time the sealing material remains bonded to the reinforcing ring and, thus, decrease the costs associated with replacing and repairing the downhole tools; and provide more effective bonding of the sealing material at elevated temperatures. Therefore, the art has sought downhole tools having a resilient material secured to an outer wall surface of a radially expansible metal ring that: increase the life of the downhole tool by increasing the length of time the sealing material remains bonded to the reinforcing ring and, thus, decrease the costs associated with replacing and repairing the downhole tools; and provide more effective bonding of the sealing material at elevated temperatures.